The present invention generally relates to substrate processing methods and apparatuses, and more particularly to a substrate processing method which carries out a process on a plurality of substrates simultaneously by carrying the substrate to a processing chamber, and to a substrate processing apparatus that employs such a substrate processing method.
When manufacturing semiconductor devices, a wafer that is used as a substrate is subjected to a cleaning process or the like by a chemical substrate surface preparation apparatus. A so-called batch type chemical substrate surface preparation apparatus is normally used because a plurality of wafers are cleaned simultaneously. But as the diameter of the wafer becomes larger, the chemical preparation chamber becomes larger, thereby increasing the size of the chemical substrate surface preparation apparatus itself. The size of other substrate processing apparatuses that carry out a predetermined process, other than the cleaning process, with respect to a plurality of substrates simultaneously, is similarly increasing.
FIGS. 1A and 1B show a first example of a conventional substrate processing apparatus. FIG. 1A is a front view showing the first conventional substrate processing apparatus in a state where wafers have been transported to a chemical chamber, and FIG. 1B is a front view showing the first conventional substrate processing apparatus in a state where the wafers are transported to the chemical chamber or are transported outside the chemical chamber. For the sake of convenience, it will be assumed that the first conventional substrate processing apparatus is a chemical substrate surface preparation apparatus for cleaning the wafers.
According to the first conventional substrate processing apparatus, a plurality of wafers 500 are accommodated within a cleaning carrier 501 and transported. A transport robot 502 holds the cleaning carrier 501 by arms 502A as shown in FIG. 1B, and moves in a direction Y1 so as to transport the cleaning carrier 501 into a chemical chamber 503 together with the accommodated wafers 500. Thereafter, the arms 502A open in directions of arrows as indicated by a dotted line in FIG. 1A, so that the cleaning carrier 501 is placed on a carrier support 504 within the chemical chamber 503. After cleaning the wafers 500, the arms 502A close from the open position indicated by the dotted line in FIG. 1A to the closed position indicated by the solid line and hold the cleaning carrier 501. The cleaning carrier 501 held by the arms 502A is moved in a direction Y2 in FIG. 1B, and the cleaning carrier 501 is transported outside the chemical chamber 503 together with the wafers 500.
As the diameter of the wafers 500 increases, the size of the cleaning carrier 501 itself increases, thereby increasing the size of the first conventional substrate processing apparatus.
On the other hand, the cleaning carrier 501 must be made of a material that does not interfere with the cleaning process, and normally, a material such as fluoric system resin or quartz is used. However, there are both advantages and disadvantages in using such materials for the cleaning carrier 501. Drawbacks that are common to the use of both of these materials are that (i) it is impossible to avoid the wafers 500 from being contaminated by the cleaning carrier 501 because the wafers 500 are accommodated within the cleaning carrier 501 and transported, (ii) the exposure of the wafers 500 is small because the cleaning carrier 501 is used and the times required for the chemical process and the washing process increase depending on the limited exposure of the wafers 500, and (iii) it is impossible to avoid the chemical from being carried outside the chemical chamber 503 when removing the wafers 500 from the chemical chamber 503 because the cleaning carrier 501 is used and the amount of the chemical used increases.
In order to overcome such drawbacks associated by the use of the cleaning carrier, so-called carrierless (or no-carrier) type substrate processing apparatuses that use no carrier have been proposed in Japanese Laid-Open Patent Applications No. 4-49619 and No. 5-36668, for example.
FIGS. 2A and 2B show a second example of a conventional substrate processing apparatus. FIG. 2A is a front view showing the second conventional substrate processing apparatus in a state where wafers have been transported to a chemical chamber. FIG. 2B is a side view showing by a dotted line the second conventional substrate processing apparatus in a state where the wafers are transported to the chemical chamber or are transported outside the chemical chamber, and showing by the solid line the second conventional substrate processing apparatus in a state where wafers have been transported to the chemical chamber. For the sake of convenience, it will be assumed that the second conventional substrate processing apparatus is a chemical substrate surface preparation apparatus for cleaning the wafers. In FIGS. 2A and 2B, those parts which are the same as those corresponding parts in FIGS. 1A and 1B are designated by the same reference numerals, and a description thereof will be omitted.
According to the second conventional substrate processing apparatus, a plurality of holding parts 502B are provided on the arms 502A of the transport robot 502. A number of grooves corresponding to the number of wafers 500 to be held are formed on the holding part 502B. When the wafers 500 are transported, each wafer 500 is held solely by the holding parts 502B. The wafers 500 transported into the chemical chamber 503 are supported by a wafer support 505 that is provided within the chemical chamber 503. A number of grooves corresponding to the number of wafers 500 to be supported are formed on the wafer support 505. The wafers 500 within the chemical chamber 503 are supported by the grooves of the wafer support 505, and the pitch with which the wafers 500 are arranged is maintained constant by the grooves.
According to the second conventional substrate processing apparatus shown in FIGS. 2A and 2B, only the wafers 500 are held and transported by the arms 502A of the transport robot 502. For this reason, compared to the first conventional substrate processing apparatus shown in FIGS. 1A and 1B, it is possible to avoid the wafers 500 from becoming contaminated by the cleaning carrier because no cleaning carrier is used. In addition, the wafers 500 are satisfactorily exposed within the chemical chamber 503 because no cleaning carrier is used, thereby requiring no additional time to carry out the chemical process and the washing process. Furthermore, since no cleaning carrier is used to remove the wafers 500 from the chemical chamber 503, it is possible to prevent the chemical from being carried outside the chemical chamber 503 when removing the wafers 500 from the chemical chamber 503, and the consumption of the chemical will not increase.
However, according to the second conventional substrate processing apparatus shown in FIGS. 2A and 2B, the plurality of separate wafers 500 must be held by the arms 502A of the transport robot 502, and the plurality of separate wafers 500 must be supported by the wafer support 505 within the chemical chamber 503. In other words, the plurality of grooves for holding the ends of the wafers 500 must be provided on the holding part 502B of the arm 502A with a high accuracy, so that each wafer 500 stand approximately straight at the constant pitch. In addition, the plurality of grooves for supporting the ends of the wafers 500 must be provided on the wafer support 505 within the chemical chamber 503 with a high accuracy, so that each wafer 500 stand approximately straight at the constant pitch within the chemical chamber 503. For these reasons, it was impossible to manufacture the holding parts 502B and the wafer support 505 at a low cost.
For example, in the case of the wafer 500 having a diameter of 6 inches and a thickness of 0.6 mm, the width of the grooves provided on the holding parts 502B of the arm 502A and on the wafer support 505 is approximately 0.8 mm. For this reason, when transporting the wafers 500 into the chemical chamber 503 or transporting the wafers 500 outside the chemical chamber 503 by the transport robot 502, there was a problem in that an extremely accurate positioning control was required so as to ensure positive catching of the wafers 500 and to prevent damage to the wafers 500 such as chipping. In addition, even if such an extremely accurate positioning control is made, the transport reliability is considerably poor compared to the first conventional substrate processing apparatus that uses the cleaning carrier. As various parts of the second conventional substrate processing apparatus deteriorate with time, the transport reliability becomes unpredictable, and the damage to the wafers 500 in an extreme case is much greater when compared to the first conventional substrate processing apparatus.
Furthermore, because the second conventional substrate processing apparatus holds the wafers 500 by the grooves of the holding parts 502B of the arm 502A and supports the wafers 500 by the grooves of the wafer support 505, there was another problem in that particles are generated by the contact between end surfaces of the wafers 500 and the grooves.
Accordingly, when the transport reliability and the positioning accuracy required of the transport robot 502 in particular are taken into consideration, the first conventional substrate processing apparatus is more preferable compared to the second conventional substrate processing apparatus. However, in addition to the drawbacks (i) through (iii) described above, the first conventional substrate processing apparatus also had a problem in that particles or dust particles that affect the yield of products using the wafers 500 are generated.
In other words, regardless of whether the material used for the cleaning carrier 501 is fluoric system resin or quartz, the cleaning carrier 501 generally includes a part that has the function of supporting the weights of the wafers 500 and a part that has the function of stopping the inclination of the wafers 500. Although the end surface of the wafer 500 looks smooth to the human eye, it has been confirmed that the end surface of the wafer 500 actually includes considerable undulations when viewed on a microscope with magnification of 2000 times. In addition, because the materials such as fluoric system resin and quartz used for the cleaning carrier 501 are softer than silicon that is used for the wafers 500, the cleaning carrier 501 is scraped and damaged by the undulations at the end surfaces of the wafers 500 every time the cleaning carrier 501 is used. More particularly, it has been confirmed that fine scratches and cracks are generated at the damaged part of the cleaning carrier 501 that supports the wafers 500.
The scratches and cracks in the cleaning carrier 501 generate the particles. It has also been confirmed that the wafers 500 become more contaminated by the particles as the number of times the cleaning carrier 501 is used increases. The contamination of the wafers 500 is caused by the particles that are generated from the cleaning carrier 501, float at the liquid surface within the chemical chamber 503, and adhere on the surface of the wafers 500 when the cleaning carrier 501 is transported into or out of the chemical chamber 503.
Accordingly, the present inventor studied the cleaning carriers 501 that have been used for a certain extent, so as to analyze the deteriorated portions of the grooves.
FIGS. 3A and 3B show an example of the cleaning carrier 501 that has been used. FIG. 3A is a plan view showing an important top part of the cleaning carrier 501, and FIG. 3B is a cross sectional view showing a vertical cross section of the cleaning carrier 501 shown in FIG. 3A viewed from the front.
A part X1 shown in FIG. 3B has the function of stopping the inclination of the wafer 500. As shown in a cross section in FIG. 4A, an end surface 500A of the wafer 500 does not make direct contact with an innermost wall portion of the cleaning carrier 501 at this part X1. Since inner walls forming the groove simply stop the inclination of the wafer 500, there is virtually no particle generation at the part X1.
On the other hand, a part X2 shown in FIG. 3B has the function of supporting the weight of the wafer 500. As shown in a cross section in FIG. 4B, the end surface 500A of the wafer 500 makes direct contact with the innermost wall portion of the cleaning carrier 501 at this part X2. Because this part X2 substantially supports the entire weight of the wafer 500, there is considerable deterioration of the inner wall of the cleaning carrier 501 due to the contact between the end surface 500A of the wafer 500 and the inner wall of the cleaning carrier 501, and considerable particle generation occurs.
FIGS. 5A and 5B show another example of the cleaning carrier 501 that has been used. FIG. 5A is a plan view showing an important top part of the cleaning carrier 501, and FIG. 5B is a cross sectional view showing a vertical cross section of the cleaning carrier 501 shown in FIG. 5A viewed from the front.
A part X3 shown in FIG. 5B has the function of stopping the inclination of the wafer 500. As shown in a cross section in FIG. BA, an end surface 500A of the wafer 500 does not make direct contact with an innermost wall portion of the cleaning carrier 501 at this part X3. Since inner walls forming the groove simply stop the inclination of the wafer 500, there is virtually no particle generation at the part X3.
On the other hand, a part X4 shown in FIG. 5B has the function of supporting the weight of the wafer 500. As shown in a cross section in FIG. 5B, the end surface 500A of the wafer 500 makes direct contact with the innermost wall portion of the cleaning carrier 501 at this part X4. Because this part X4 substantially supports the entire weight of the wafer 500, there is considerable deterioration of the inner wall of the cleaning carrier 501 due to the contact between the end surface 500A of the wafer 500 and the inner wall of the cleaning carrier 501, and considerable particle generation occurs.
Therefore, both the first and second conventional substrate processing apparatuses have advantages and disadvantages. Hence, there was a problem in that the particles are generated by the use of the cleaning carrier 501 and the wafers 500 are contaminated by the particles or, that extremely accurate positioning control is required when transporting the wafers 500 by the transport robot 502 so that the wafers 500 are positively caught.